Psychometric properties of the Danish Parental Stress Scale: Rasch analysis in a sample of mothers with infants

The Parental Stress Scale (PSS) was developed as a short measure of perceived stress resulting from being a parent. The current study examined the psychometric properties of the Danish version in a sample of 1110 mothers of children aged 0 to 12 months using Rasch models. Emphasis was placed on the issues of uni-dimensionality and absence of differential item functioning relative to the age and educational level of the mothers. Results showed that no adequate fit could be established for the full PSS scale with 18 dichotomized items. Further analyses showed that items 2 and 11 had to be eliminated from the scale, and that the remaining items did not make up a unidimensional PSS scale, but two subscales measuring different aspect of parental stress: a 9-item scale measuring parental stress and a 7-item scale measuring lack of parental satisfaction. Fit to the Rasch model could not be established for any of the two subscales. For the parental stress subscale, we found evidence of local dependence for four item pairs (3 and 4, 9 and 10, 10 and 16, 12 and 16), as well as evidence of two items functioning differentially: item 16 relative to level of education, and item 3 relative to both age and educational level. For the lack of parental satisfaction subscale, we found evidence of local dependence between some two pairs (1 and 17, 17 and 18), but no evidence of differential item functioning. Both subscales fit graphical loglinear Rasch models adjusting for local dependence and differential item functioning. Plotting the adjusted subscale scores against one another showed that the two-scale solution provides additional information, as some mothers are stressed but not lacking in parental satisfaction.